This invention relates generally to the controlled cooling of the molten flat glass ribbon as it passes through the tin float bath at a continuous rate. Manufacturing flat glass comprises the delivering of molten glass to a bath of molten tin and advancing the glass along the surface of the tin under thermal conditions that do not contaminate the internal atmosphere. Such contamination is detrimental to both the glass product and the molten tin. Glass at approximately 1900 degrees F enters the bath from the melting tank and at approximately 1200 degrees F exits the bath to a cooling lehr. In prior art installations the temperatures in the bath are maintained with electrical resistance heaters suspended from the roof over the ribbon of glass. Such electrical heaters do not contaminate the bath atmosphere. The metal plate shell of the prior art bath roof is protected from the heat with an internal refractory lining, which has little or no heat-insulating qualities and isolates the electrical equipment plenum above from the heated cavity. This prior art construction has been used over the past twenty-five year period. Attempts to burn natural gas over the bath by the glass industry failed the industry's contamination requirements.
______________________________________ Patents Number Date Relationship ______________________________________ 3,083,551 04.02.63 Layout of float bath with molten metal 3,332,763 07.25.67 Layout of tin float bath utilizing electrical heating elements 3,486,869 12.30.69 Layout of tin float bath utilizing regular and auxiliary electrical heating elements ______________________________________
Reference Material (To assist in understanding the presentation)
The Handbook of Glass Manufacture, volume II, 3rd edition, pages 714-2 through 714-21.
The Glass Industry Magazine, April 1980 issue, pages 18,20,22, article "Float Glass Production: Pilkington vs PPG," by Ronald A. McCauley, Rutgers University.
A Review Lecture, "The float glass process,"by L. A. B. Pilkington, delivered Feb. 13, 1949.
Reference Drawings, sheet 1 with FIGS. 1 and 2 and sheet 2 with FIG. 3 showing the existing electrical tin float bath.
Prior art uses electrical heating elements with intricate power supplies, conductors, contactors and controls. The present invention's use of a natural gas system with automatic recuperative burners surpasses the prior art by being more cost-efficient and more energy-efficient, does, not contaminate the bath atmosphere, is more easily installed, minimizes maintenance and shutdown, all of which promotes increased productivity.